General PhilosophyGeneral PhilosophyDr Peter Millican, Hertford CollegeDr Peter Millican, Hertford College

Lecture 5:Lecture 5:Knowledge and ScepticismKnowledge and Scepticism

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From Scepticism to KnowledgeFrom Scepticism to Knowledge

Sceptical arguments, such as those of Sceptical arguments, such as those of Descartes, suggest that we know very little. Descartes, suggest that we know very little. But we still want to distinguish between But we still want to distinguish between things that we consider we have a right to things that we consider we have a right to believe (e.g. on the basis of experience or believe (e.g. on the basis of experience or strong testimony), and other less secure strong testimony), and other less secure beliefs (e.g. “superstitions”).beliefs (e.g. “superstitions”).If the sceptical arguments can’t be If the sceptical arguments can’t be answered, then it’s tempting to attack the answered, then it’s tempting to attack the problem by (re-?) defining “knowledge”.problem by (re-?) defining “knowledge”.

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What is Knowledge?What is Knowledge?

““What is X?” questions:What is X?” questions:– X might be “truth”, “perception”, “reason”, “the X might be “truth”, “perception”, “reason”, “the

mind”, “personal identity”, “freedom”, etc.mind”, “personal identity”, “freedom”, etc.– Seen as important in Philosophy since Plato.Seen as important in Philosophy since Plato.

But they are puzzling. Are we asking:But they are puzzling. Are we asking:– ““When do we apply the word ‘X’?” When do we apply the word ‘X’?” oror– ““What is a What is a genuinegenuine case of X?” case of X?”

The former seems merely linguistic; the The former seems merely linguistic; the latter – if different – can appear senseless.latter – if different – can appear senseless.

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What is Geography?What is Geography?

““Geography” as a discipline:Geography” as a discipline:– Initially, perhaps, described the study of places Initially, perhaps, described the study of places

in terms of location, physical characteristics, in terms of location, physical characteristics, mineral resources, natural flora and fauna etc.mineral resources, natural flora and fauna etc.

– Then extended to cover land-use, farming, and Then extended to cover land-use, farming, and other economic factors, even culture …other economic factors, even culture …

– Suppose one were now to ask “But is culture Suppose one were now to ask “But is culture reallyreally part of the discipline of geography?” part of the discipline of geography?”

– Well, if “geography” as actually used does Well, if “geography” as actually used does cover the study of culture, the answer is “Yes!”cover the study of culture, the answer is “Yes!”

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The Concept of KnowledgeThe Concept of Knowledge

Core Core normativenormative concept, concept, versusversus particular particular judgements:judgements:– The concept of “knowledge” plays a central role in The concept of “knowledge” plays a central role in

distinguishing distinguishing reliablereliable beliefs from others. beliefs from others.– This makes it This makes it normativenormative: calling something : calling something

“knowledge” does more than just categorising it as “knowledge” does more than just categorising it as something we standardly something we standardly callcall knowledge. knowledge.

– Hence it does seem to be possible to ask Hence it does seem to be possible to ask “Everyone “Everyone callscalls this knowledge, but is it this knowledge, but is it reallyreally?”?”

– Compare the response to Strawson on induction: Compare the response to Strawson on induction: we we callcall it reasonable, but is it it reasonable, but is it reallyreally good evidence? good evidence?

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Intuitions, Puzzle Cases, and Intuitions, Puzzle Cases, and Conceptual AnalysisConceptual Analysis

Conceptual analysis can involve:Conceptual analysis can involve:– Appeal to linguistic “intuitions” (i.e. judgements Appeal to linguistic “intuitions” (i.e. judgements

that we are naturally inclined to make).that we are naturally inclined to make).– Puzzle cases (“intuition pumps”) that can put Puzzle cases (“intuition pumps”) that can put

pressure on those intuitions.pressure on those intuitions.– Argument, in which we draw out implications of Argument, in which we draw out implications of

these plausible judgements and principles.these plausible judgements and principles.– Systematisation, in which we try to clarify the Systematisation, in which we try to clarify the

concept coherently in the light of all this.concept coherently in the light of all this.

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Three Kinds of KnowledgeThree Kinds of Knowledge

AcquaintanceAcquaintance– ““I know Oxford”, “Do you know John Smith?”.I know Oxford”, “Do you know John Smith?”.

Knowing HowKnowing How– ““I know how to drive”, “Do you know how to open I know how to drive”, “Do you know how to open

this?”this?”

Knowing ThatKnowing That, or , or Propositional KnowledgePropositional Knowledge– ““I know I know thatthat this building is the Exam Schools”, this building is the Exam Schools”,

“Do you know “Do you know thatthat it will rain?” it will rain?”– Where Where PP is the proposition concerned, this is is the proposition concerned, this is

often referred to as “Knowledge that often referred to as “Knowledge that PP”.”.

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The Traditional Analysis of The Traditional Analysis of Knowledge that Knowledge that PP

A subject (i.e. a person) A subject (i.e. a person) SS knows that knows that PPif, and only if:if, and only if:– PP is true is true– SS believes that believes that PP– SS is justified in believing that is justified in believing that PP

A.J. Ayer gives the last two conditions as:A.J. Ayer gives the last two conditions as:– SS is sure that is sure that PP is true is true– SS has the right to be sure that has the right to be sure that PP is true is true

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PP is true is true

If If SS knows that knows that PP, does it follow that , does it follow that PP must be must be truetrue? Distinguish two claims:? Distinguish two claims:

– SS knows that knows that PP → → PP is necessarily true is necessarily truefalsefalse: I know that I exist, but it doesn’t follow that I : I know that I exist, but it doesn’t follow that I exist necessarily.exist necessarily.

– Necessarily ( Necessarily ( SS knows that knows that PP → → PP is true ) is true )convincingconvincing: We wouldn’t allow : We wouldn’t allow S’S’s belief that s belief that PP to to be counted as a case of be counted as a case of knowledgeknowledge unless the unless the belief is, in fact, belief is, in fact, truetrue. So it is a necessary truth that . So it is a necessary truth that anything known is true.anything known is true.

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Complications?Complications?

Knowing Falsehoods?Knowing Falsehoods?– ““I know that France is hexagonal”I know that France is hexagonal”

In a sense this can be considered true, because In a sense this can be considered true, because France is France is roughlyroughly hexagonal, but in that same hexagonal, but in that same sense, it is also true that France is hexagonal.sense, it is also true that France is hexagonal.

An AbominationAn Abomination– NeverNever confuse “ confuse “PP is true” with “ is true” with “PP is is believedbelieved to be to be

true”. true”. Don’tDon’t say “ say “PP is true for me, but is true for me, but PP is false for is false for him” when what you mean is simply “I believe him” when what you mean is simply “I believe PP, , but he does not”. It was never but he does not”. It was never truetrue than the Sun than the Sun orbits the Earth, even when everyone thought so!orbits the Earth, even when everyone thought so!

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SS believes that believes that PP

If If SS knows that knows that PP, does it follow that , does it follow that SS believes that believes that PP? Not so clear:? Not so clear:– Reliable guessingReliable guessing

Suppose that I am not aware of knowing anything Suppose that I am not aware of knowing anything about some topic, but my “guesses” in a quiz are about some topic, but my “guesses” in a quiz are always accurate. I might be reported as always accurate. I might be reported as knowing knowing PP, even though I don’t believe , even though I don’t believe PP..

– BlindsightBlindsightSomeone with blindsight has no conscious visual Someone with blindsight has no conscious visual awareness, but can “guess” fairly reliably when awareness, but can “guess” fairly reliably when asked to point towards objects.asked to point towards objects.

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Knowing that One KnowsKnowing that One Knows

Suppose that knowledge must always be Suppose that knowledge must always be “conscious”. Then if I know that “conscious”. Then if I know that PP, will it , will it follow that I must know that follow that I must know that I know that P?I know that P?– The principle is tempting, but we can iterate …The principle is tempting, but we can iterate …

I know that I know that PPI know that I know that I know that PI know that PI know that I know that I know that I know that PI know that I know that PI know that I know that I know that I know that I know that PI know that I know that I know that P … …

– It is clearly impossible to have conscious belief It is clearly impossible to have conscious belief in all of this infinite sequence.in all of this infinite sequence.

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SS is justified in believing that is justified in believing that PP

Perhaps the central role of the concept of Perhaps the central role of the concept of knowledge is to distinguish between beliefs knowledge is to distinguish between beliefs that are “secure” and those that aren’t.that are “secure” and those that aren’t.So what makes the difference between:So what makes the difference between:– believingbelieving that that PP (where (where PP happens to be true) happens to be true)– knowingknowing that that P?P?

““Surely”, if a belief that Surely”, if a belief that PP is to count as a is to count as a case of case of knowledgeknowledge, it must be a , it must be a justifiedjustified belief: one must have belief: one must have the rightthe right to believe it. to believe it.

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The Regress of JustificationThe Regress of Justification

Suppose that I believe that Suppose that I believe that PP, and this belief is to , and this belief is to be justified. Its justification will typically involve be justified. Its justification will typically involve other beliefs. But then if other beliefs. But then if PP is to be justified, these is to be justified, these other beliefs must be justified too, and so on … ?other beliefs must be justified too, and so on … ?How to prevent an infinite regress? We could take How to prevent an infinite regress? We could take the whole web of interlocking beliefs as mutually the whole web of interlocking beliefs as mutually justifying in some way justifying in some way (coherentism),(coherentism), or else some or else some beliefs must be justified in a way that does not beliefs must be justified in a way that does not depend on any other belief. Descartes was a depend on any other belief. Descartes was a foundationalistfoundationalist, taking some beliefs to be totally , taking some beliefs to be totally secure. A more modern approach is secure. A more modern approach is externalismexternalism..

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Internalism and ExternalismInternalism and Externalism

An An internalistinternalist account of justification requires all account of justification requires all relevant factors to be relevant factors to be cognitively accessiblecognitively accessible to to SS. . We’ll see that this faces difficulties …We’ll see that this faces difficulties …An An externalistexternalist account (e.g. Armstrong, Goldman) account (e.g. Armstrong, Goldman) allows that some factors relevant to judging allows that some factors relevant to judging S’S’s s justification (for belief that justification (for belief that PP) can be ) can be inaccessibleinaccessible to to SS; or ; or externalexternal to to S’sS’s cognitive perspective. cognitive perspective.So justification could be a matter of a So justification could be a matter of a reliablereliable causal link between facts and beliefs. I might causal link between facts and beliefs. I might know that know that PP (because my belief reliably depends (because my belief reliably depends on on PP’s truth) without knowing ’s truth) without knowing howhow I know. I know.

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Gettier CasesGettier Cases

Suppose that:Suppose that:– SS is justified in believing that is justified in believing that P.P.– PP clearly implies clearly implies QQ..

Does it follow that Does it follow that SS, after inferring , after inferring QQ from from PP, is justified in believing that , is justified in believing that QQ??On internalist interpretations of “justified”, On internalist interpretations of “justified”, this does seem to follow. But it leads to this does seem to follow. But it leads to so-called “Gettier counterexamples” to the so-called “Gettier counterexamples” to the traditional analysis of knowledge.traditional analysis of knowledge.

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A Gettier-style CounterexampleA Gettier-style Counterexample

MirageMirage Real OasisReal Oasis(out of sight)(out of sight)

S’S’s belief is true, and apparently justified, since he infers it s belief is true, and apparently justified, since he infers it from the (apparently justified) belief that he can see an oasis. from the (apparently justified) belief that he can see an oasis. But we would not say he But we would not say he knewknew that there’s an oasis there. that there’s an oasis there.

““There’s an oasis There’s an oasis over there”over there”

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““No Dependence on False Beliefs”No Dependence on False Beliefs”

Should we add a fourth condition? For example, Should we add a fourth condition? For example, SS knows that knows that P P if, and only if:if, and only if:– PP is true is true– SS believes that believes that PP– SS is justified in believing that is justified in believing that PP … …– … … in a way that doesn’t depend on any falsehoodin a way that doesn’t depend on any falsehood

But this seems too strong. If you tell me “there But this seems too strong. If you tell me “there were exactly 78 people there”, but you slightly were exactly 78 people there”, but you slightly miscounted (in fact there were 77), can’t I miscounted (in fact there were 77), can’t I knowknow that there were more than 40 people there, even that there were more than 40 people there, even though I’ve inferred this from a falsehood?though I’ve inferred this from a falsehood?

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The Lottery ParadoxThe Lottery Paradox

Another approach would be to understand Another approach would be to understand justification as involving justification as involving very high probabilityvery high probability of of truth (given the evidence available to truth (given the evidence available to SS).).But then consider a billion-ticket lottery:But then consider a billion-ticket lottery:– I believe that ticket 000000000 won’t winI believe that ticket 000000000 won’t win– I believe that ticket 000000001 won’t winI believe that ticket 000000001 won’t win

……– I believe that ticket 999999999 won’t winI believe that ticket 999999999 won’t win

Each of these is Each of these is extremelyextremely probable, but we’re probable, but we’re reluctant to call any of them “knowledge”. So it reluctant to call any of them “knowledge”. So it seems that no probability threshold will do.seems that no probability threshold will do.

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Non-Accidental TruthNon-Accidental Truth

To deal with the lottery paradox, it’s plausible To deal with the lottery paradox, it’s plausible to count a belief as to count a belief as knowledgeknowledge only if it’s not only if it’s not an an accidentaccident – not a “mere” matter of chance – not a “mere” matter of chance (of whatever numerical degree) – that it’s true.(of whatever numerical degree) – that it’s true.But how do we pin this down?But how do we pin this down?– Is it mere “chance” that my corroding speedometer is Is it mere “chance” that my corroding speedometer is

still sufficiently reliable to provide an accurate reading still sufficiently reliable to provide an accurate reading (when perhaps in a month’s time it won’t be)?(when perhaps in a month’s time it won’t be)?

– Suppose I very occasionally hallucinate that Suppose I very occasionally hallucinate that PP, is it , is it “chance” that my current perceptual belief that “chance” that my current perceptual belief that P P is not is not an hallucination?an hallucination?

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ContextualismContextualism

Yet another problem, especially pressing for an Yet another problem, especially pressing for an “internalist” account of knowledge, is that “internalist” account of knowledge, is that sometimes our criteria can vary.sometimes our criteria can vary.– ““I know that the train leaves at 17:36” (because I I know that the train leaves at 17:36” (because I

always take that train).always take that train).– ““But do you really But do you really knowknow that it does? It really is that it does? It really is

essential that I make that appointment.”essential that I make that appointment.”– ““OK, I’ll check on the Web to make sure. Then I’ll OK, I’ll check on the Web to make sure. Then I’ll

know.”know.”This suggests that the “hurdle” for what counts as This suggests that the “hurdle” for what counts as adequate justification can vary.adequate justification can vary.

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The Role(s) of the Concept of The Role(s) of the Concept of KnowledgeKnowledge

Consider the contrast between:Consider the contrast between:““Does Does sheshe know that her husband is cheating know that her husband is cheating on her?”on her?”

which could just mean “Does she believe that he’s which could just mean “Does she believe that he’s cheating on her, as we all do?”cheating on her, as we all do?”

““Do you Do you knowknow that her husband is cheating on that her husband is cheating on her?”her?”

which is more likely to mean “Is it genuinely the which is more likely to mean “Is it genuinely the case?”, rather than an epistemological enquiry.case?”, rather than an epistemological enquiry.

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Is “Knowledge” a Genuine Category?Is “Knowledge” a Genuine Category?

It is very unusual, in ordinary life, to ask It is very unusual, in ordinary life, to ask “Does “Does SS know that know that PP” in a situation where:” in a situation where:– We are totally confident that We are totally confident that SS believes that believes that P;P;andand– We are totally confident that We are totally confident that PP is true. is true.

This might suggest that it’s a mistake to This might suggest that it’s a mistake to search for some single consistent account of search for some single consistent account of what “knowledge” is, which can deal with all what “knowledge” is, which can deal with all the contexts in which it is applied.the contexts in which it is applied.But we can still ask whether But we can still ask whether PP is true … is true …

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Back to G.E. Moore’s HandsBack to G.E. Moore’s Hands

If we agree with Moore, then we may see If we agree with Moore, then we may see externalism about knowledge and externalism about knowledge and justification as a way of reconciling his justification as a way of reconciling his claim that we claim that we knowknow this is a hand, with the this is a hand, with the sceptical arguments that seem to show sceptical arguments that seem to show that we can’t that we can’t know that we knowknow that we know..An externalist can say to the sceptic:An externalist can say to the sceptic:

““I can’t prove to you that I know this is a hand, I can’t prove to you that I know this is a hand, or that my belief is justified, but nevertheless I or that my belief is justified, but nevertheless I claim that I do know it, and it is justified.”claim that I do know it, and it is justified.”

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Externalism and ScepticismExternalism and Scepticism

Suppose we accept an externalist account of Suppose we accept an externalist account of justification. So justification. So ifif, say, my perceptual beliefs , say, my perceptual beliefs are, are, in factin fact, caused by a reliable causal , caused by a reliable causal processprocess, then, then I do in fact know that this table I do in fact know that this table is in front of me.is in front of me.But of course the sceptic can still ask: “How But of course the sceptic can still ask: “How do I do I knowknow – or if you prefer, – or if you prefer, what right do I what right do I have to be at all confidenthave to be at all confident – that my beliefs – that my beliefs are in fact so caused?” Externalism does not are in fact so caused?” Externalism does not exclude sceptical doubt “from the inside”.exclude sceptical doubt “from the inside”.

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Putnam’s Semantic ExternalismPutnam’s Semantic Externalism

The sceptic claims “I might be a brain in a The sceptic claims “I might be a brain in a vat (BIV), so this hand might be just part of vat (BIV), so this hand might be just part of the image created artificially.”the image created artificially.”But what do I But what do I meanmean by “hand”? According by “hand”? According to Putnam, meanings aren’t purely mental.to Putnam, meanings aren’t purely mental.If I am a BIV, then my word “hand” If I am a BIV, then my word “hand” actuallyactually means a “hand-in-the-image” …means a “hand-in-the-image” …… … in which case this in which case this isis genuinely a “hand”, genuinely a “hand”, because it is a hand-in-the-image.because it is a hand-in-the-image.

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Sceptical Responses (1)Sceptical Responses (1)

Is the meaning of “hand” just determined by Is the meaning of “hand” just determined by what we’re what we’re actuallyactually referring to when we think referring to when we think we’re pointing to a real hand?we’re pointing to a real hand?Or do we have some further idea of the kind Or do we have some further idea of the kind of thing that a hand of thing that a hand really isreally is??Can we thus make sense of the possibility of Can we thus make sense of the possibility of a “God’s eye view” (unavailable to us), from a “God’s eye view” (unavailable to us), from which it would be clear that it is all a clever which it would be clear that it is all a clever simulation, rather than involving a real entity simulation, rather than involving a real entity something like what we take a hand to be?something like what we take a hand to be?

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(2) Post-Linguistic Envatting(2) Post-Linguistic Envatting

Suppose that I am “envatted” Suppose that I am “envatted” afterafter I have I have become linguistically competent.become linguistically competent.So then my word “hand” has already So then my word “hand” has already established its “outside vat” meaning.established its “outside vat” meaning.It seems to follow that when I later say “this It seems to follow that when I later say “this is a hand” from within the vat, I can manage is a hand” from within the vat, I can manage to mean a to mean a realreal hand rather than a mere hand rather than a mere “hand-in-the-image”. If so, I can raise the “hand-in-the-image”. If so, I can raise the question as to whether question as to whether thisthis really is a really is a handhand..

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Back to InductionBack to Induction

With With verticalvertical scepticism (evil demon, BIV, scepticism (evil demon, BIV, The The MatrixMatrix etc.), it’s tempting to ask in a semantic etc.), it’s tempting to ask in a semantic externalist spirit: “Why should I externalist spirit: “Why should I carecare if it’s all an if it’s all an illusion? I’m quite happy to continue with ‘life illusion? I’m quite happy to continue with ‘life as I experience it’ either way.”as I experience it’ either way.”But Hume’s “problem of induction”, as a form of But Hume’s “problem of induction”, as a form of horizontalhorizontal scepticism, evades this response: scepticism, evades this response: whether the world I experience is real or not, I whether the world I experience is real or not, I still have the problem of inferring from past to still have the problem of inferring from past to future, from “observed” to “not yet observed”.future, from “observed” to “not yet observed”.

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The Ethics of BeliefThe Ethics of Belief

Hume avoids indiscriminate scepticism by Hume avoids indiscriminate scepticism by rejecting Descartes’ “ethics of belief” – the view rejecting Descartes’ “ethics of belief” – the view that we should withhold assent to anything that we should withhold assent to anything that’s not known with total certainty.that’s not known with total certainty.Hume sees belief as typically Hume sees belief as typically involuntaryinvoluntary, so , so withholding assent isn’t even an option.withholding assent isn’t even an option.Note that epistemological externalism also Note that epistemological externalism also involves a similar rejection.involves a similar rejection.We seem to be forced to accept this, if we are We seem to be forced to accept this, if we are to hold out against the sceptic.to hold out against the sceptic.